Both my husband and my sister are know-it-alls who try to do everything without knowledge or ability to do so. My husband wants to remove my dogs sutures to save money. My sister's motivations are often the same--to save money. What is this person called?
I have some singularly unflattering suggestions for you.
For the medically pretentious overtones: Quack
a person who pretends, professionally or publicly, to skill, knowledge, or qualifications he or she does not possess; a charlatan.
More of the fraudster type: Charlatan
A person falsely claiming to have a special knowledge or skill:
a self-confessed con artist and charlatan
Perhaps the most neutral of the bunch: Pretender
a person who makes unjustified or false claims, statements, etc., as about personal status, abilities, intentions, or the like:
a pretender to literary genius.